Immersion plating consists of dipping or submerging a metal component into a nonconductive bath of metal solution ions causing a replacement reaction. With immersion plating, no external current is needed. Due to the differing nobilities of the base metal and the metal ions, the base metal will be displaced by the ions of a higher nobility which resist being in a soluble state.
One of the most common uses of immersion plating is silver on copper. When a copper component – such as a bus bar – is immersed in the silver electrolyte, the silver ions reduce to silver metal and deposit onto the copper substrate. Once the copper is completed coated with silver, the deposition is halted.
As with other selective plating applications, an immersion silver can be applied to a localized area of a component. It is imperative that this localized area remains saturated for an extended period of time in order for the deposit to form.
A properly cleaned copper part immersed in, or saturated with, the solution for up to two minutes should achieve an average deposit thickness of 5 μin to 8 μin. While a silver immersion solution plates well at room temperature, operating parameters such as pH, temperature, and solution flow will affect the transfer dynamic, increasing the reaction rate at the plating surface.
Applications for Immersion Silver
Immersion silver is used for a variety of applications, including:
- Lower contact resistance
- Improve solderability
- Protection from oxidation
While immersion silver is inexpensive and gives the appearance of a silver plating, it does not provide the full functionality of an electroplated deposit. Due to the low thicknesses achieved and the poor adhesion, silver immersion deposits do not meet many required specifications.
For more information on SIFCO ASC’s silver plating products and services, please contact us at firstname.lastname@example.org or 800-765-4131.